scholarly journals A Probabilistic Approach to Assessing and Predicting the Failure of Notched Components

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4053 ◽  
Author(s):  
Miguel Muñiz-Calvente ◽  
Lucas Venta-Viñuela ◽  
Adrián Álvarez-Vázquez ◽  
Pelayo Fernández Fernández ◽  
María Jesús Lamela Rey ◽  
...  
Keyword(s):  
Probabilistic Approach ◽  
Experimental Results ◽  
Cumulative Distribution ◽  
Experimental Program ◽  
Component Design ◽  
Reliable Assessment ◽  
Three Samples ◽  
Notch Geometry ◽  
Failure Predictions ◽  
Notched Components

This work presents a probabilistic model to evaluate the strength results obtained from an experimental characterisation program on notched components. The generalised local method (GLM) is applied to the derivation of the primary failure cumulative distribution function (PFCDF) as a material property (i.e., independent of the test type, load conditions and specimen geometry selected for the experimental campaign), which guarantees transferability in component design. To illustrate the applicability of the GLM methodology, an experimental program is performed using specimens of EPOLAM 2025 epoxy resin. Three different samples, each with a specific notch geometry, are tested. As a first scenario, a single assessment of each sample is obtained and the PFCDFs are used to perform cross predictions of failure. Some discrepancies are noticeable among the experimental results and cross-failure predictions, although they are within the expected margins. A possible reason for the disagreement can be assigned to the inherent statistical variability of the results and the limited number of tests per each sample. As a second scenario, a joint assessment of the three samples is performed, from which a unique PFCDF is provided, according to the GLM. In the latter case, a more reliable assessment of the experimental results from the geometry conditions is achieved, the suitability of the selected driving force is verified, and the transferability of the present material characterisation is confirmed.

scholarly journals Multi-Sensor Fusion for Aerial Robots in Industrial GNSS-Denied Environments

2021 ◽  
Vol 11 (9) ◽  
pp. 3921
Author(s):  
Paloma Carrasco ◽  
Francisco Cuesta ◽  
Rafael Caballero ◽  
Francisco J. Perez-Grau ◽  
Antidio Viguria
Keyword(s):  
Sensor Fusion ◽  
Computational Efficiency ◽  
Probabilistic Approach ◽  
Laser Scanner ◽  
Industrial Applications ◽  
Experimental Results ◽  
Added Value ◽  
Aerial Robots ◽  
3D Localization ◽  
High Level

The use of unmanned aerial robots has increased exponentially in recent years, and the relevance of industrial applications in environments with degraded satellite signals is rising. This article presents a solution for the 3D localization of aerial robots in such environments. In order to truly use these versatile platforms for added-value cases in these scenarios, a high level of reliability is required. Hence, the proposed solution is based on a probabilistic approach that makes use of a 3D laser scanner, radio sensors, a previously built map of the environment and input odometry, to obtain pose estimations that are computed onboard the aerial platform. Experimental results show the feasibility of the approach in terms of accuracy, robustness and computational efficiency.

The Use of Strain Energy and Fracture Correlation to Determine Life Expectancy for Notched Components

2009 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross ◽  
M.-H. Herman Shen
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Cross Section ◽  
Strain Energy ◽  
Notch Root ◽  
Stress Gradient ◽  
Strain Curve ◽  
Experimental Results ◽  
Cyclic Process ◽  
Notched Components

An energy-based method for predicting fatigue life of half-circle notched specimens, based on the nominal applied stress amplitude, has been developed. This developed method is based on the understanding that the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where the density of each can be determined by measuring the area underneath the monotonic true stress-strain curve and measuring the sum of the area within each Hysteresis loop in the cyclic process, respectively. Using this understanding, the criterion for determining fatigue life prediction of half-circle notched components is constructed by incorporating the stress gradient effect through the notch root cross-section. Though fatigue at a notch root is a local phenomenon, evaluation of the stress gradient through the notch root cross-section is essential for incorporating this method into finite element analysis minimum potential energy process. The validation of this method was carried out by comparison with both notched and unnnotched experimental fatigue life of Aluminum 6061-T6 (Al 6061-T6) specimens under tension/compression loading at the theoretical notch fatigue stress concentration factor of 1.75. The comparison initially showed a slight deviation between prediction and experimental results. This led to the analysis of strain energy density per cycle up to failure, and an improved Hysteresis representation for the energy-based prediction analysis. With the newly developed Hysteresis representation, the energy-based prediction comparison shows encouraging agreement with unnotched experimental results and a theoretical notch stress concentration value.

Determination of Permeability Properties of Concrete Surface Modified by CPF

2015 ◽  
Vol 732 ◽  
pp. 389-392 ◽  
Author(s):  
Pavel Reiterman
Keyword(s):  
Surface Layer ◽  
Water Transport ◽  
Concrete Surface ◽  
Experimental Results ◽  
Experimental Program ◽  
Functional Characteristics ◽  
Concrete Permeability ◽  
Surface Modified ◽  
Durability Of Concrete

The paper introduces an experimental program focused on the monitoring of water transport in surface layer of concrete aimed at monitoring the permeability of concrete, since concrete permeability is a property uniquely affecting durability of concrete. Introduced methods are complemented by experimental results and other traditional tests. These findings will serve to further optimization of the structure being created, thus ensuring its better aesthetic and functional characteristics.

scholarly journals Structural Behavior of Concrete Beams Containing Recycled Coarse Aggregates under Flexure

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
In-Hwan Yang ◽  
Jihun Park ◽  
Kyoung-Chul Kim ◽  
Hyungbae Lee
Keyword(s):  
Experimental Data ◽  
Flexural Strength ◽  
Concrete Beams ◽  
Crack Pattern ◽  
Crack Spacing ◽  
Experimental Results ◽  
Structural Behavior ◽  
Experimental Program ◽  
Coarse Aggregates

The structural behavior of concrete beams containing recycled coarse aggregates (RCAs) was investigated in this study using detailed experimental data. Twelve concrete beams were tested in the experimental program: nine beams with varying RCA contents and three control beams with natural coarse aggregates (NCAs). The parameters for investigating the structural behavior of the RCA concrete beams under flexure were the RCA content (30%, 50%, and 100%) and tensile rebar ratio (0.50%, 0.79%, and 1.14%). The crack pattern of the RCA beams was similar to that of the NCA beams; however, the RCA beams exhibited smaller crack spacing than the NCA beams. The flexural strength was slightly affected by the RCA content. However, the ductility of the beam was not significantly influenced by the RCA content. A comparison of the experimental results and the calculations from the ACI 318 and EC 2 provisions for the flexural strength showed that the current provisions conservatively predicted the flexural strength of the RCA concrete beams.

A Transonic Compressor Stage: Part 2 — CFD Simulation

2004 ◽  
Author(s):  
G. V. Hobson ◽  
A. J. Gannon ◽  
R. P. Shreeve
Keyword(s):  
Cfd Simulation ◽  
Pressure Ratio ◽  
Internal Flow ◽  
Design Tool ◽  
Experimental Results ◽  
Navier Stokes ◽  
Experimental Program ◽  
Compressor Stage ◽  
Transonic Compressor ◽  
Cfd Method

The simulation of a transonic compressor stage is presented. This stage was designed using an Euler CFD code with the intent of minimizing the use of empirical design techniques. The stage has subsequently been built and tested. More recently an existing multi-block Navier-Stokes code with a steady averaging-plane to pass information between the blade rows was used to simulate the flow through the machine. Performance maps of stage pressure ratio and efficiency at 70, 80, 90 and 100% speeds from both the Euler and Navier-Stokes CFD codes are compared with the experimental results. Details of the internal flow from the Navier-Stokes code are presented. Comparison of the design Euler CFD and experimental results showed reasonable agreement and validated its use as a design tool. Agreement between experimental and the current Navier-Stokes CFD results was good, allowing the code to be used in the viewing of the internal flow field. Improvements to the initial design CFD method are discussed in light of the experimental program and more recent simulations.

Effect of Creep Relaxation on the Delayed Hydride Cracking Behavior of Irradiated Zirconium 2.5%Wt Niobium Pressure Tube Material

2006 ◽  
Author(s):  
Heather Chaput ◽  
Brian W. Leitch ◽  
Don R. Metzger
Keyword(s):  
High Stress ◽  
Local Stress ◽  
Operating Conditions ◽  
Experimental Results ◽  
Pressure Tube ◽  
Experimental Program ◽  
Tube Material ◽  
Cracking Behavior ◽  
Delayed Hydride Cracking ◽  
Hydride Cracking

Surface scratches and flaws encountered in CANDU nuclear pressure tubes must be evaluated to ensure that a cracking mechanism, called delayed hydride cracking (DHC), is not initiated. The stress concentration due to a flaw can cause diffusion of hydrogen and precipitation of zirconium hydride at the flaw tip. The presence of a hydride results in reduced fracture resistance in a local region where high stress prevails. In many cases, flaws exist for an extended period of time before the hydrogen content in the base material is sufficient to form a hydride. In this situation high stress creep can significantly relax the local stress at the flaw tip. The assessment of flaws on the basis of local stress distribution not considering creep is expected to be overly conservative, and may result in unnecessary remedial action in reactor operation and maintenance procedures. An experimental program has been developed to isolate and quantify the effect of creep on DHC in irradiated Zr-2.5%Nb pressure tube material. As part of this program, the thermal and load histories relevant to reactor operating conditions have been considered, and initial experimental results indicate that the action of creep increases the threshold load for crack initiation. Finite element analysis of creep relaxation around a hydride also supports the experimental results, and a fracture initiation model is applied to the experimental conditions in order to establish an analytical trend for the effect of creep. The quantitative effect predicted by the model is in reasonable agreement with the experimental results, and an improved, less conservative assessment procedure that accounts for creep is deemed to be practical.

The Measurement of Component Friction Losses in a Fired Engine: Part 2 — Experimental Results

2005 ◽  
Author(s):  
Riaz A. Mufti ◽  
Martin Priest
Keyword(s):  
Engine Performance ◽  
Cost Effective ◽  
Operating Conditions ◽  
Experimental Results ◽  
Engine Oil ◽  
Sensor Technology ◽  
Component Level ◽  
Component Design ◽  
Engine Part ◽  
Actual Use

Bench testing can provide rapid and cost effective information for developing new lubricants. But there is general agreement that the only satisfactory means of evaluating the behaviour of engine oil is by actual use in engine. Also for detailed analysis of the tribological interaction it is important to analyse the engine performance at the component level. With the help of advance data acquisition system and sensor technology, experimental measurement of friction losses at the component level have been measured at realistic engine operating conditions, using the technique explained in Part 1. This paper describes the outcome of the experimental results at a range of engine operating conditions using mainly SAE 0W20 lubricant and some results from a friction-modified SAE 5W30 lubricant. The results clearly show considerable changes in the percentage contribution of power loss between low and high lubricant temperatures. The change in mode of lubricating regime from boundary to fluid film lubrication can be seen at the component level with increase in engine speed and decrease in lubricant temperature. This system can be used as a powerful tool for screening engine oils, analysing component design, validating friction models and studying the effect of different additives on the performance of each component under realistic operating conditions.

Probabilistic Integrity Assessment of Corroded Gas Pipelines

2006 ◽  
Vol 128 (4) ◽  
pp. 547-555 ◽  
Author(s):  
Sang-Min Lee ◽  
Yoon-Suk Chang ◽  
Jae-Boong Choi ◽  
Young-Jin Kim
Keyword(s):  
Probabilistic Approach ◽  
Bending Moment ◽  
Combined Loading ◽  
Gas Pipelines ◽  
Index Method ◽  
Integrity Assessment ◽  
Assessment Program ◽  
Simulation Techniques ◽  
Reliable Assessment ◽  
Assessment Procedures

Pressurized gas pipelines are subject to harmful effects from both the surrounding environments and the materials passing through them. Reliable assessment procedures, including fracture mechanics analyses, are required to maintain their integrity. Currently, integrity assessments are performed using conventional deterministic approaches, even though there are many uncertainties to hinder rational evaluations. Therefore, in this study, a probabilistic approach was considered for gas pipeline evaluations. The objectives are to estimate the failure probability of corroded pipelines in the gas and oil industries and to propose operating limit conditions for different types of loadings. To achieve these objectives, a probabilistic assessment program was developed using reliability index method and simulation techniques, and applied to estimate the failure probabilities of corroded API-5L-X52/X60 gas pipelines subjected to internal pressure, bending moment, and combined loading. The operating limit conditions as well as prototypal evaluation and sensitivity analysis results showed a promising applicability of the probabilistic integrity assessment program.

Behavior of Foam Particles Lightweight Concrete with Time

2018 ◽  
Vol 8 (04) ◽  
Author(s):  
Sohila A. El-Khouly ◽  
Amr H. Zaher ◽  
Ehab F. Sadek ◽  
Khalid M. Hilal
Keyword(s):  
Lightweight Concrete ◽  
Load Level ◽  
Experimental Results ◽  
Time Dependent ◽  
Flexural Behavior ◽  
Unit Weight ◽  
Experimental Program ◽  
Sustained Load ◽  
Polystyrene Foam ◽  
Loading Test

Lightweight Concrete with polystyrene foam particles (LWC) was obtained through the use of polystyrene foam as a partial aggregate’s replacement to reduce the concrete dry unit weight from 23 KN/m3 to 18.50 KN/m3. This research presents an experimental and theoretical investigation in the long-term behavior of LWC in compression and flexure. Two experimental programs were conducted; namely, creep and shrinkage of LWC under compressive loading test, and the time-dependent flexural behavior of reinforced LWC beams. The main variable in the first experimental program was the percentage of sustained load, while the main variables in the second experimental program were the percentage of sustained load and the percentage of compression reinforcement. Experimental results showed that LWC exhibits a significantly higher time-dependent strain (shrinkage plus creep) than normal weight concrete (NWC) under sustained compressive load and at the same compressive strength, with an increasing percentage about 9%. The creep strains of LWC seemed to be proportional to the stress to strength ratio. The timedependent deflections of the LWC beams were higher than those of NWC beams with increasing percentage about 25%. Addition of compression steel reinforcement (As`) to LWC beams reduced time-dependent deflections. Sustained load level and LWC time-dependent deflection were directly proportional. Finally, models and equations proposed by different codes were used to evaluate the obtained experimental results. From the theoretical study, it was found that Bazant-Baweja B3 Model gave superior shrinkage strains prediction for LWC. The ACI 209R-92 presented preferable predictions of creep strain and time-dependent deflection of LWC.

Seismic Investigation of Steel Pile Bents: II. Retrofit and Vulnerability Analysis

2002 ◽  
Vol 18 (1) ◽  
pp. 143-160 ◽  
Author(s):  
Ayman A. Shama ◽  
John B. Mander ◽  
Stuart S. Chen
Keyword(s):  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Vulnerability Analysis ◽  
Experimental Results ◽  
Experimental Program ◽  
Seismic Investigation ◽  
Seismic Vulnerability Analysis ◽  
Plastic Steel

This paper is the second of a two-part study on the seismic vulnerability of deck bridges supported on steel pile bents. A conceptual elastic cap/elasto-plastic steel pile retrofit strategy is proposed in this part with the aim of strengthening the connection and ensuring plastification takes place only in the steel pile. An experimental program was carried out to assess the retrofit strategy. On the basis of the experimental results for existing as well as retrofitted connections, a seismic vulnerability analysis for bridges supported by steel pile bents was performed. Fragility curves for such structures were developed using a simplified fundamental mechanics-based approach. The study showed that the retrofitted connections exhibited superior energy absorptions with respect to the existing connections. Fragility curves also demonstrated the effectiveness of the retrofit strategy proposed.

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